Error message is not user-friendly when user tries to compile a query and pass string for startkey and endkey

If user do not add quotes to string key error appears:
{"error":"bad_request","reason":"invalid UTF-8 JSON: error,{1,\"lexical error: invalid char in json text.\\n\",\n \"simple\"}"}
but there is no invalid char, just the string is not quoted.

Steps:
1. create some doc with string key ('simple' in my case)
2. create some view
3. go to view page and enter just simple in startkey parameter
4. perform query